A Christian is beloved of God and a sinner. How can these two contradictions be harmonized: I am a sinner and deserve God's wrath and punishment, and yet the Father loves me? Christ alone can harmonize these contradictions. He is the Mediator.
For all who rely on works of the law are under a curse; for it is written, “Cursed be everyone who does not abide by all things written in the Book of the Law, and do them.” Now it is evident that no one is justified before God by the law, for “The righteous shall live by faith.” But the law is not of faith, rather “The one who does them shall live by them.” Christ redeemed us from the curse of the law by becoming a curse for us—for it is written, “Cursed is everyone who is hanged on a tree”—so that in Christ Jesus the blessing of Abraham might come to the Gentiles, so that we might receive the promised Spirit through faith. (Galatians 3:10-14 ESV)
The Accent of ‘For Us’
Paul does not say that Christ was made a curse for Himself. The accent is on the two words “for us.” Christ is personally innocent. Personally, He did not deserve to be hanged for any crime of His own doing. But because Christ took the place of others who were sinners, He was hanged like any other transgressor. The Law of Moses leaves no loopholes. It says that a transgressor should be hanged. Who are the other sinners? We are. The sentence of death and everlasting damnation had long been pronounced over us. But Christ took all our sins and died for them on the Cross. “He was numbered with the transgressors; and he bare the sin of many, and made intercession for the transgressors.” 
All the prophets of old said that Christ should be the greatest transgressor, murderer, adulterer, thief, blasphemer that ever was or ever could be on earth. When He took the sins of the whole world upon Himself, Christ was no longer an innocent person. He was a sinner burdened with the sins of a Paul who was a blasphemer; burdened with the sins of a Peter who denied Christ; burdened with the sins of a David who committed adultery and murder, and gave the heathen occasion to laugh at the Lord. In short, Christ was charged with the sins of all men, that He should pay for them with His own blood. The curse struck Him. The Law found Him among sinners. He was not only in the company of sinners. He had gone so far as to invest Himself with the flesh and blood of sinners. So the Law judged and hanged Him for a sinner.
I am told that it is preposterous and wicked to call the Son of God a cursed sinner. I answer: If you deny that He is a condemned sinner, you are forced to deny that Christ died. It is not less preposterous to say, the Son of God died, than to say, the Son of God was a sinner.
Whatever sins I, you, all of us have committed or shall commit, they are Christ's sins as if He had committed them Himself. Our sins have to be Christ's sins or we shall perish forever.
If Christ bears our sins, we do not bear them. But if Christ is innocent of our sins and does not bear them, we must bear them, and we shall die in our sins. “But thanks be to God, which giveth us the victory through our Lord Jesus Christ.”  When we hear that Christ was made a curse for us, let us believe it with joy and assurance. By faith Christ changes places with us. He gets our sins, we get His holiness.